INDUSTRIAL *™ HIGH SCHOOLS 



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LEEDS 




D.^VAN NOSTRAND COMPANY 

PUBLISHERS NEW YORK 




Class T*3S3 

Book „ • ._: 



Copyright N°_ 



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COPYRIGHT DEPOSIT: 



MECHANICAL DRAWING 

FOR 

INDUSTRIAL and HIGH SCHOOLS 



BY 

CHARLES C. LEEDS 

Professor of Mechanical Drawing 

School of Applied Industries 
Carnegie Institute of Technology 



THIRD PRINTING — THOROUGHLY REVISED 




NEW YORK 

D. VAN NOSTRAND COMPANY 

1915 



First Issued in 1908 

as 

The High School Edition of 

Mechanical Drawing fcr Trade Schools 

Reprinted in 1912 



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COPYRIGHT. 1908 
BY 

D. VAN NOSTRAND COMPANY 



COPYRIGHT, 1915 
BY 

D. VAN NOSTRAND COMPANY 



Vo" 



THE 

VAN NOSTRAND PRESS 

NEW YORK 



MQV | 1915 

©CI.A414356 



PREFACE 



THIRD EDITION 



It is seven years since this work was first published, and the 
author feels very grateful for the generous manner in which it has 
been received. 

In the preface of the first edition we emphasized the need of 
teaching Mechanical Drawing by a method which should develop 
the student's creative faculties. We desire strongly to reaffirm 
this position, as these years of added experience have strengthened 
our belief in the vital importance of stimulating the student's 
imagination. 

We have added considerable new subject matter and have pre- 
sented certain fundamentals in much clearer form than in the pre- 
vious edition. 

In presenting the subject of Isometric Projection, the illustration 
Fig. 1 8 is original with us, as we have never before seen the relation- 
ship between Mechanical and Isometric shown in this simple fashion. 



We have taken out the lessons on Gearing and Intersections and 
Developments, under the belief that most High School students 
gain little of real value from these subjects as they are generally 
taught. We believe that these subjects can be handled to much 
better advantage in a Technical School or College. 

We are attempting to place certain theories before teachers of 
Mechanical Drawing by means of a "Letter" placed at the beginning 
of the text. This plan is due to the desire on our part to make 
clear our aims to those who use this work as a text or reference 
book. 

We have tried to correct all the errors in the previous editions 
and shall be grateful to those who may call our attention to any 
mistakes discovered in this one. 

Charles C. Leeds. 

May 15. 1915. 



A LETTER TO DRAWING TEACHERS 



To help the boys of secondary schools to a realization that 
Mechanical Drawing is a Language, to assist them in learning to 
read and write this Language and to stimulate and strengthen then- 
imagination, these are the primary aims of this book. 

These toys should be taught that mechanical drawings are used 
in a large portion of the commercial enterprises to which they will 
look for employment when their school days are over, and that a 
clear knowledge of this subject has considerable value in the business 
world. 

The fac" that so many boys are obliged to leave school as soon 
as the law permits, makes it all the more imperative that, while 
they are still in school, they shall be given instruction that will 
prepare them for their future as wage earners. 

Those boys who are able to continue their studies should be bene- 
fited as well, from the fact that, if they can acquire the fundamentals 
of mechanical drawing while in a secondary school, they may take 
more advanced work when entering a Technical School or College. 

We have tried to lay out this work in such manner as to lead 
the student along by easy steps, taking him from one basic prin- 
ciple to the next as he is able to grasp the subject. 

The instruction should be individual as far as possible, for much 
better results can be obtained by this method than by trying to 
carry a group of students along, all on the same lesson, regardless 
of their varying ability. 

The use of models in teaching the elements of mechanical draw- 



ing should be discouraged, as the practice tends to prevent the 
development of the creative imagination. This faculty of forming 
mental pictures of various forms of construction is very essential 
to all who would use mechanical drawings to the best advantage. 

Models are valuable when teaching free-hand sketching, as 
they give an added interest to the work by making it seem more 
like the conditions under which commercial work is done. 

Where the teacher has difficulty in making the student understand 
the shape of an object from a mechanical drawing, it is preferable 
to show an isometric or perspective sketch of the object as an aid, 
rather than a model, as this will help the student more clearly to 
see the distinction between these two methods, mechanical and per- 
spective, and will also help to develop his imagination. 

One of the serious handicaps carried by a large element of the 
entering classes in Technical Schools is the lack of imagination. 
The development of this faculty is absolutely essential if a man is 
to use to the fullest extent his powers for creative work. 

Contrary to general belief this faculty is as necessary to the 
successful business man as to the artist and writer. It is there- 
fore the hope of the author that this book may be of value as an 
aid in developing the boys imagination and, to the same extent, 
his reasoning powers. 

To give force to the theory we have advanced in regard to the 
value of developing the imagination, the author begs leave to quote 
the following from a great modern psychologist : 



A LETTER TO DRAWINCx TEACHERS— Continued. 



"There is an identity of nature between the constructive im- 
agination of the mechanic and that of the artist: the difference is 
only in the end, the means and the conditions. . . Taken as a 
whole, its psychological mechanism is the same as that of any 
other creative work." 

In preparing the text matter we have treated the subjects rather 
briefly in most cases, with the thought in mind that we may count 
on the teacher's giving more elaborate explanation of the prin- 
ciples involved where it is necessary. 



In closing we wish to recommend very strongly that the teacher, 
when giving aid to the student on his drawings, use the "Induction 
Method." That is, do not give a direct answer to the student's 
appeal for help, but try to help him, by suggestion, to see for himself 
the solution of his difficulty. 

This method requires patience and resourcefulness on the part 
of the teacher, but it also has the desired advantage of stimulating 
the student's reasoning powers. 

The Author. 



LESSON No. 1. 



MECHANICAL DRAWING.— A Mechanical Drawing is an 
instrument used to convey exact information from one person to 
another. Generally speaking it is a graphic illustration of some 
mechanism or form of construction used in the commercial life 
around us. 

A mechanical drawing represents the written form of a Language 
that is a commercial necessity. This language ma}' be described 
as a ''pictorial" one, as it is by means of a drawing, showing one 
or more views of an object, that we furnish the necessary information 
as to the shape and size of this object. 

Mechanical drawings are in constant use in some form in the 
business world with which our lives are brought into daily con- 
tact, consequently this is a modern language that we should 
know something of if we wish to make the most of our opportunities 
when we take up commercial work. 

To be able clearly to understand mechanical drawings, we must 
learn to read and write this language after the manner in use in 
commercial life. This means that we must become familiar with 
the principles upon which the subject is founded. 

Mechanical drawings, as the name indicates, are made mechan- 
ically, that is, with instruments, as distinguished from drawings 
made freehand. 

The instruments included in a simple set vary greatly, but in 
the main consist of a pencil compass, a pair of dividers, a ruling 
pen, and a compass pen. The instruments mentioned are those 
that are actually necessary, but more elaborate sets should be ob- 
tained where one's means will permit, as the expenditure is justi- 
fiable on account of the greater convenience and ease in making 
good drawings. 



In addition to the instruments mentioned, each student needs 
a T-square, scale, 45-degree triangle, 30-60 degree triangle, drawing 
pencils, an eraser and thumb tacks. 

Plain pear-wood T-squares are satisfactory and inexpensive. 
One with a 24-inch blade is long enough for this work. 

A flat 12-inch scale graduated in i6ths on one edge and 32ds 
on the other is most suitable for our purpose, as the fractions used 
on most mechanical drawings are multiples of these numbers. A 
scale with white edges and dark graduation lines is highly desirable, 
as the use of this type is least tiresome for the eyes. 

Triangles of some transparent material, such as celluloid, are 
most satisfactory, though many draftsmen use triangles made of 
pear or cherry wood. A 7-inch 45 triangle (° degree sign) and a 
9-inch 30°-6o° triangle will be found large enough for our purpose. 

The hardness of the lead in drawing pencils is usually indicated 
by a number before the letter H, as 2H, 3H, 4H, etc.; the higher 
the number the harder the lead in the pencil. 

For the students of secondary schools, 4H pencils will be found 
quite satisfactory when making their mechanical drawings, as this 
grade of pencil will hold a point for a reasonable length of time 
and will also make a fairly dark line. For freehand work, such as 
lettering, putting on dimensions and sketching, nothing harder 
than 2H should be used. 

One of the best erasers is the Emerald No. in, though the 
Ruby No. 112 is just as good. 

The common manila drawing papers are very satisfactory and 
are inexpensive. These papers are used more than any others in 
commercial drafting rooms. Paper n inches by 15 inches in size will 
be found large enough for all lessons. 



LESSON No. 1— Continued. 



The drawing board should be made of soft wood; white pine or 
yellow poplar are preferable where they can be obtained, as it is 
easier to push in and pull out the thumb tacks which hold the 
drawing paper. For all this work a board 18 inches by 24 inches 
is amply large. 

Small thumb tacks are much to be preferred to large ones, as they 
hold the paper as well and are more easily pushed into or drawn from 
the board. 

PENCIL. — Having selected the drawing pencil most suitable for 
our purpose (4H) let us prepare it for use. First we cut away the 

Round not straight. 





Do this with your knife. 



File the point. 

Fig. i. 




wood as shown in the illustration, Fig. 1, then the lead is sharpened 

by rubbing it over a strip of sandpaper mounted on a piece of 

wood, or on a smooth, single cut file. 

About 1 inch from the end of the pencil, beginning on one of 

the six corners, cut away the wood in a clean manner so as to bare 

about f inch of the lead ; then sharpen by sliding the lead over the 

surface of the file or sandpaper, 
turning the pencil as it is moved 
along, so as to produce a round 
point. 

The other end of the 4H 
pencil should be sharpened to 
a flat point. To produce this 
point enter the knife about 
1 inch from the end of the 
pencil on one of the flat sides 

(not corner), and cut away the wood in the manner shown in the 

illustration, Fig. 2, baring about § inch of the lead. 




Fis. 2. 




Fig. 3. 



To sharpen the lead, slide it back and forth along the file, form- 
ing a chisel-like point. 

The round point is used in setting off dimensions and for lining 
in all the finished lines of the drawing, while the flat point is used 
mainly for light, thin construction lines, center lines, etc. 

The 2H pencil should be sharpened 
at one end only, in a fashion similar to 
the round point of the drawing pencil, 
though not so sharp a point is needed 
as on the latter. 

PAPER. — Drawing paper should be 
fastened to the board as smoothly as 
possible, for it is very difficult to do 
satisfactory work on paper which does 
not lie flat on the board. 

Use small thumb tacks to fasten down the paper, placing them 
in the order shown in the illustration, Fig. 3. Push the tacks well 
down, so that the heads bind the paper closely; this will also enable 
the T-square to be slipped over them easily without knocking small 
chips out of the edge of the blade. 

DRAWING BOARD. — T-SQUARE. — TRIANGLES. — The 
Drawing Board should be somewhat larger than the paper used, 
and the surface upon which the paper is mounted should be smooth 
and flat. As the left-hand edge of the board is the one against 
which we place the T-square head, this edge must be perfectly 
straight, as well as smooth and free from bumps or high spots. 

The upper edge of the T-square blade and the inside edge of the 
head should be perfectly straight, and be smoothly and accurately 
finished. These two surfaces are set at a right angle with each 
other; in other words, they form an angle of 90 . 

When using these tools the head of the square is held against 
the left-hand edge of the board and the upper edge of the blade 
used as a ruling edge for all horizontal lines. For vertical lines, 
hold square as mentioned above, also hold one of the triangles 



LESSON No. 1.— Continued. 



as shown In the illustration, Fig. 4, and use the left-hand edge of 
the triangle for a ruling edge, always drawing the pencil away from 
square blade when ruling a line. 

To rule lines properly, lean the top of the pencil slightly away 
from the ruling edge so that the pencil point will slide along in the 
corner formed by the ruling edge and the surface of the paper. 

MEASUREMENTS. — The student must become familiar with 
the scale used in making measurements, as this part of the work 
is of the greatest importance in making accurate drawings. 

The simplest plan to follow in laying off a given length is, first 



to rule a light, thin line (generally termed a construction line) 
in the proper position, then place the edge of the scale just against 
the line; now mark small pencil points on the line, directly opposite 
the graduations in the scale which indicate the desired length. 
Now using the square or triangle as a ruling edge, make the line 
heavy between the two points and the result is the finished line 
of the proper length. 

La}- out ten horizontal lines just 6| inches long, ten vertical 
lines 5! inches long, and ten 45° lines 4^ inches long. These lines 
may be any suitable distance apart. 




LESSON No. 2. 



DRAWING TO MEASUREMENTS.— We will use the T-square, 
one triangle, the scale and the pencil for this lesson, and the student 
should keep in mind the fact that the main purpose of our present 
lesson is to increase his knowledge of these tools and his skill in 
using them, with special emphasis laid on the use of the scale. 

When laying off measurements for the following figures, great 
care must be used to get the sizes exact, as the student should not 
be satisfied with any work but the very best he can produce. 

Lay out an 8-inch square, that is, a figure whose four sides are 
each 8 inches long. A good plan to follow is to draw in the sides 
with light, thin lines first, then when the proper sizes are measured 
off, to run over the lines again, making the outline of the square 
heavy. Also lay out a 4-inch and a 2-inch square on the same sheet 
of paper. 

Draw a light line diagonally across each square, that is, a line 
from far corner to far corner, or the longest straight line that can 
be drawn inside of each square. On this diagonal line lay off points 
or measurements as follows; for the 8-inch square these points 



should be \ inch apart, starting at one corner and letting the last 
measurement come what it will, on the 4-inch square make the 
points ys inch apart and on the 2-inch square f inch between points. 
Now using the T-square and 45 ° triangle, with the triangle as the 
ruling edge, draw light lines through these points in each square, 
these lines to be at right angles to the diagonal line. 

When drawing in these lines care must be taken to see that they 
cut the center of the point, and the finished 
result should be three figures similar to that 
shown in Fig. 5. 

It is rather preferable that the student 
should finish completely one square at a 
time. 

One feature of the work that we desire 
to emphasize is that the student should 
study the instruction sheets of each lesson 
very carefully; he should try to learn the purpose of the lesson 
and its important points before attempting to make the drawing. 




Fig. 5. 



LESSON No. 3. 



COMPASS POINTS.— Our first duty is to prepare the com- 
pass points for use. If possible use compasses that have a needle 
point similar to that shown in Fig. 6. The end with the shoulder 
should be used, as by its use large center holes are eliminated. 



as shown in the illustration, Fig. 7, set the compass points to a 
measurement or radius of \ inch, then holding compass as shown 





n 



\ 



Fig. 6. 



Set the lead pencil J to f inch out from the end of the compass 
leg; now with the file produce a flat point somewhat like a chisel 
point (except that it is dressed off on both sides) ; this flat pencil 
point should be set at right angles to the needle point and about 
even with the shoulder of the latter. 

After adjusting the lead properly, file off the corners of the flat 
point as shown in Fig. 6, and the result should be a fairly narrow 
flat pencil point, which is slightly shorter than the needle point. 

The preparation of the compass points is of considerable im- 
portance and should be done carefully if accurate work is expected. 

Taking the compass in the right hand and the scale in the left, 




Fig. 7. 



in Fig. 8, throw in a i-inch circle. Test for accuracy by measuring 
the finished circle with the scale. 



LESSON No. 3— Continued. 



Cover the drawing paper with circles, beginning with the i-inch 
circle described, making each circle a little larger than the previous 
one. Set the compass points very carefully to the dimensions on 
the scale before making each circle, then use the scale to measure 
the finished work. 

The purpose of this lesson is to familiarize the student 
with the use of the compass, with special emphasis laid on its 



preparation for use and the setting to measurements from the 
scale. 

The student should not underestimate the value of properly 
prepared drawing pencil and compass pencil points, and he should 
make it a rule always to keep them in good order. Neat, accurate 
drawings are a necessity and properly kept tools are a great aid 
in their production. 




Fig. 8. 



LESSON No. 4 



Fillet 



ROUNDED CORNERS.-FILLETS.-In the construction of 
machinery of various types it is a common practice to round some 
of the comers of the castings and of many other parts that make 
up the machines. Where the round corner is formed at the junc- 
tion of two surfaces, as shown in Fig. 9, it is termed a 

fillet. 

The surfaces joined by these round corners may 

form any angle; consequently we should select a 

method of throwing in radii, or rounding the corners, 

•which will apply to all corners. 

The method suggested, for lack of a better name, 

we have given the title "trial method," as it is by 
1 — ' trial that we locate the position of the compass needle. 

FlG ' 9 ' When finding the center of the radius, place the 

compass in s*ch a position that the lead point rests directly upon 
one of the corner lines, then rest the needle point lightly on the 
paper in the position which the eye indicates as the center Now 
balance the compass lightly on the needle point and swing the lead 
point around to the other corner line; if this point comes directly 
on the line, the needle position is correct and the radius maybe 
thrown in. If the position is not quite right, swing the lead point 
back to the original line, balance on this, and shift the needle 




t,oint the amount judged to be necessary. By this method, and 
with a little practice, the student should become quite proficient in 
locating the radius center without loss of time. 

For the purpose of demonstrating the value of the above method 
of throwing in radii, it is desired that the student shall make a 
drawing of the following figures: _ 

Using b>ht, thin construction lines, lay out a 4 -mch square 
an equilateral triangle with 5-inch sides, and a rhombus with 5-Hich 
sides The smaller angle between the sides of the latter is to be 45 ■ 
These figures should be arranged so that all three may be placed 
on the same sheet of drawing paper. 

Having laid out these figures in light, thin lines, set the com- 
pass to a *-inch radius and, after finding the center by trial, round 
the corner's of each. Remember that when finding the compass 
needle position it must be set in such a manner that the lead comes 
just on the construction line and blends with it. _ 

Make these round corner lines fairly heavy when throwing them 
in, then line in the rest of the figure, making the whole outlme of 

the same thickness. 

The trial method of finding radius centers is advantageous from 
the fact that it applies equally well to all angle corners, and tends 
to promote speed in production. 



LESSON No. 5. 



CONSTRUCTION CIRCLES.— Certain figures are of such 
shape that they are of considerable value as aids in constructing 
the drawings of other figures. The circle is used for this purpose 
constantly, as it is a great help when it is desired to lay out quickly 
and accurately such figures as the square, the hexagon, etc. 

Both shopmen and draftsmen make use of the circle as an aid 
to lay out these figures. Their methods of use differ, mainly because 
these two departments use different tools for laying out their work. 
Usually the shopman will inscribe the figure desired inside the 
circle, while the draftsman will circumscribe it outside of the circle. 

When the figure is inscribed within the circle, the diameter of 
the circle is equal to the diameter of the figure across corners, or 
its greatest diameter. When the figure circumscribes the circle, 
the diameter of the circle is equal to the diameter across flats, or 
the short diameter of the figure. 

It is desired that the student shall draw the following figures, 
using both of the above mentioned methods: 

Inscribe a square within a 2xf-inch circle and a hexagon within 
a 2 j^-inch circle. 

Draw two 2-inch circles, circumscribe one with a square and 
the other with a hexagon figure. All of these construction circles 
should be formed of light lines. 

When inscribing the square within the 2jf-inch circle, use the 
T-square and one triangle to draw two light construction lines 
across the circle. These lines must be placed at right angles to each 



other and the point where they intersect must be the center of the 
circle. 

The four points formed by these two lines crossing the circle are 
the corners of the square; connect these points with firm, clear 
lines and the square is complete. 

To inscribe the hexagon in the 23^-inch circle, set the dividers 
to the radius of the circle and with this step off six points around 
the circle. If this is done carefully the circumference will be divided 
into six equal parts, as the radius of the circle equals the chord of 
one-sixth of the circumference. Connect these six points with firm, 
clear fines and the hexagon is complete. 

To circumscribe one of the 2-inch circles with a square, use 
the T-square and the 45 ° triangle (the latter to be the ruling edge) 
to draw in the lines which form the sides of the square. These lines 
must blend with the circle, that is, each line should touch the 
circle at one point only and the finished result should be a square 
of firm, clear lines, with a faint-lined construction circle just touch- 
ing each of the four sides. 

The circumscribed hexagon figure should be laid out in the 
same manner as the square, with the exception that the student 
should use the 3o°-6o° triangle as a ruling edge for drawing in the 
sides. 

The principles of construction used in this lesson are constantly 
applied in commercial work and they are well worth the student's 
earnest attention. 



LESSON No. 6. 



NUTS. — This lesson is an application of the principles of con- 
struction given in 'our previous lesson, that is, the use of the circle 
as an aid to lay out these figures. 

The method to be followed is that of the draftsman, and the 
student is expected to make a full-size drawing of the two nuts shown. 

The large circle shown in the top view in each case is used as 
a construction circle; it is also customary to show this circle as a 
means of indicating that the corners of the nuts are chamfered, 
or rounded off. 

HEXAGON NUT.— Lay off the center lines first, so that the 
positions of the views are fixed at the beginning. Arrange the 
positions of the views of the two nuts upon the paper so that their 
appearance is pleasing, as taste in such matters is of considerable 
value. 

Lay out the top view before the others, as from this we may 
project the edge and side views. 

Set the compass correctly and throw in the construction circle 
representing the diameter across flats. Then, with T-square and 
30°-6o° triangle, rule in the hexagon outline. 



Next, project light construction lines (lines any length) from 
the sides and corners of the top view to assist in drawing the side 
and edge views. After measuring the height of nut and throwing 
in the radii, line in the part of these construction lines that is needed 
and erase the balance. Finish the outlines of all three views neatly 
and put in the dimension lines and the dimensions. 

SQUARE NUT. — The same method of procedure is followed 
for the square nut as that just described for the hexagon nut, except 
that we use the 45 ° triangle for a ruling edge when outlining the 
top view. 

Lay out the top view first and make use of it as an aid in con- 
structing the edge view. This is a fundamental principle, which is 
to be followed as a general rule with pieces of such shape that we 
can make use of this advantage. 

In certain respects there is something lacking as regards the 
correctness of these views of the nuts illustrated, but the student 
may ignore this with the understanding that the main purpose of 
this lesson was to make an application of the principle of construc- 
tion featured in our previous lesson. 




Side 




class Industrial 

name John W. Roberf-s date Feb- 6-/5. 



The Carnegie Institute or Technology 

PITTSBURGH, PA. 



Nuts 



scale Full Size 



ows.no.C-IOOO 



LESSON No. 7. 



LETTERING. — The average stuc'ent does not fully appreciate 
the value of being able to letter well, and while he is seldom 
pleased with his lettering, he usually coes not like to devote 
the necessary time to practice. A great many young draftsmen 
reach the point where they are able to make a neat, workmanlike 
drawing, the appearance of which they will spoil when they letter 
and dimension it. 

In making a study of the types of letters illustrated, take especial 
notice of the oval, which is the r asis of most of the lower-case letters, 
and observe the proportions of this type; note also the slope of both 
types. 

The capitals are used mainly for titles and headings, while the 
lower-case letters are used for all notes shown on drawings and for all 
other purposes, except for titles and headings. 

As an aid in learning to letter, it is well to use guide lines as shown 



in the illustration. The student will find the slope guide lines a great 
help also in making letters of uniform appearance. 

FIGURES. — What has been written in regard to lettering applies 
equally well to figures. 

It is of great importance t 1 at the student s v ould learn to make his 
figures so well that no one s % ould have any trouble in reading them 
easily and quickly. Mistakes in the shops are very frequently caused 
by poorly written figures on drawings, and these mistakes are often 
very costly. The value of using great care at all times in placing the 
dimensions on drawings is thus clearly shown. 

THE LESSON. — Make a neat pencil copy of the illustration, 
using care with both letters and figures; note carefully the proportions 
of both. Leave off figures showing spacing of guide lines, as these 
were intended merely as an aid to the student in laying put his lessor 
sheet. 




class . Industrial 

HAtut John W. Roberts OAt£ : Nosr„ 12,0$ 



The Carnegie: Institute of Technology 

PITTSBURGH, PA. 



Lettering - Figures 

SCALE Full S&6 • DW6.NO.C.I0QI 



LESSON No. 8. 



MACHINE BOLT. — Make a full-size three-view mechanical 
drawing of the i^-inch machine bolt shown in the illustration, Drawing 
C-1002. View (a) represents the end of the bolt head as seen from 
the position of (a). View (b) is a side view of the bolt and hexagon 
nut. View (c) is an end view of the threaded end of the bolt and of 
the hexagon nut as seen from the position of (c). The positions of 
the views are given in relation to the edges of the paper. 

THE DRAWING.— Lay off the center lines first, so that the 
positions of the views are fixed at the beginning; do not let them 
"happen" as regards location. 

In drawing view (a), lay out the 2^-inch construction circle, and 
then with the T square and 45 triangle, draw in the outline of the head. 

View (c) is drawn in the same manner, that is, first the 2|-inch 
construction circle, then, using the T square and the 30°-6o° triangle 
draw the outline of the hexagon nut, and finally throw in the i^-inch 
circle to represent the end of the bolt. 

Having drawn views (a) and (c), now lay off the lengthwise dimen- 
sions of view (b), and draw vertical construction lines through these 
points (lines any length). With the T square, project the horizontal lines 
of the bolt from the end views, these lines to be light construction lines, 
until their true length is known. Now swing in the various radii, 
make them as heavy as the final outline is to be, and line in the bolt 



and nut completely, so that the whole outline stands out clearly and 
distinctly. 

SCREW THREADS.— The threaded end of the bolt is indicated 
by alternate light and heavy lines, the heavy lines being shorter than 
the light ones. This is a conventional method of indicating screw 
threads, and it has the merit of being easily understood and is inex- 
pensive. 

While it is not essential that the space between the light lines should 
be just the same as the pitch of the thread, or that the lines should be 
sloped at exactly the correct angle, it is of considerable importance 
that the threaded surface as a whole should look approximately 
correct. 

When the slope is correct for a single-thread screw, a line drawn at 
right angles to the center line of the screw should touch the end of one 
of the thread lines at one side and pass midway between that line and 
the next at the opposite side, as indicated by the light dash line d-e. 
In other words, the slope equals half of the pitch of the thread. 

Place the dimensions just as shown in the illustration, and make 
the figures carefully, so that there can be no doubt as to their meaning. 
The dimensions which refer to the position of the different views 
should be left off, as they were intended to aid the student in locating 
the views, and have no other value. 




class Industrial 

hamc John W. Roberts date Feb. P0_ 06. 



The Carnegie: Institute or Technology 

PITTSBURGH, PA. 



Machine Bolt 

scale. Full Size owg.no. C-f 002 



LESSON No. 9. 



HIDDEN SURFACES.— Until the present time we have been 
using lines which could be seen on the surface, or which repre- 
sented the surface of the figures that we have used as subjects for 
our drawing lessons. " : 

In mechanical drawing it is constantly necessary to show by 
some means, surfaces or details of parts that are hidden from view 
behind the surface shown by solid lines. 

Unless these surfaces could be indicated by some simple method, 
it would often be necessary to make additional drawings, or at least, 
additional views to show clearly the shape of the figure illustrated. 

The method commonly used to indicate these hidden surfaces 
is to draw them in, in the proper positions, but to use lines formed 
of short dashes. These dash lines or "hidden lines," as they are 
generally called, have a distinctly different appearance from the 



solid outlines of the rest of the drawing, and their meaning should 
be readily understood. 

THE LESSON. — Make a full-size three-view pencil drawing 
of the clamp shown on Drawing C-1003. Finish the drawing in a 
neat, attractive manner, using care to see that no dimensions are 
left off. 

These three views represent the side, the end, and the bottom 
of the clamp. The shape of the clamp or what it is used for is of 
no importance in our present lesson, as our purpose in using this 
piece is merely to illustrate the hidden surface lines. 

These hidden surface lines are the essential feature of this lesson, 
and as this type of line is in constant use on mechanical drawings, 
it is highly desirable that the student shall have a clear understand- 
ing of the subject. 



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Class Industrial 

name John W.Roberts date Oct. 6-06. 



The Carnegie Institute or Technology 

PITTSBURGH, PA . 



Clamp 



scale Full Size 



CnG./Ve.C-/0G3 



LESSON No. 10. 



SECTIONING. — When making drawings it is often necessary 
to show at least one view of the piece or pieces illustrated, with 
part cut away, or "in section," as it is generally termed. 

The advantage of this plan is that it helps to show the shape 
of the piece more clearly, and often the dimensions can be placed 
to better advantage on a sectional view. 

As an aid in indicating that a piece is in section, the surface 
cut is covered with light lines called "section lines." These lines 
are drawn with the aid of a 45° triangle as a ruling edge, the triangle 
being held against the T-square blade and moved for each line. 

In this course of lessons we will use the type of sectioning shown 
on Drawing C-1004, for all metals, the only variation being that 
the lines should be spaced close together for small pieces and farther 
apart for large ones. 

In commercial work it is an economic advantage to follow this 



method of sectioning, and to indicate by other means than the 
section lines the kind of metals to be used for the machine parts 
shown on drawings. 

Where two or more pieces assembled together are shown in 
section, the different parts are shown more clearly by sloping the 
section lines in opposite directions where the parts join. 

Where no special section is indicated, it is usually understood 
that the cut is made along the center line of the view from which 
the sectional view is projected. In this lesson the section is taken 
on the vertical center line of the end view. 

THE LESSON. — The important feature of this lesson is the 
principle of showing a piece in section. 

Make a two-view pencil drawing of the hollow sleeve illus- 
trated. Use care to finish the drawing neatly, putting into practice 
the various fundamentals given in previous lessons. 





cl/*3j Industrial 
«ue John W Roberts 



date Oct. 24-06. 



The Carnegie: Institute of Technology 

PITTSBURGH, PA. 



Sleeve 



scale. Full Size 



oiA/a. no. C- 1604 



LESSON No. 11. 



ORTHOGRAPHIC PROJECTION.— The natural impulse of 
most boys when attempting to make a freehand drawing of an 
object, is to try to represent the object as it appears to their eye. 
In other words, they make a one plane drawing which shows two or 



Plane 




View point 



Fig. io. 

three faces or sides of an object in the one view, similar to the 
way the Vee Block is shown in Fig. io. 

Drawings made after the fashion of Fig. io are known as per- 
spective drawings, and while this type of drawing has its place 
in commercial work, the method is not suitable for use by manu- 
facturers of various forms of mechanical construction. 

Fig. io represents the object as seen from one viewpoint only. 

A mechanical drawing represents an object as seen from several 
different viewpoints, as many as are necessary to get a clear idea 
of the shape of the object. 

Instead of one view showing several faces of an object, a me- 
chanical drawing shows a view for each face desired, and these 



views are arranged in relation to each other according to certain 
laws of projection, in the manner shown by Fig. n. 

Mechanical drawings are suitable for the purposes of manu- 
facturers, because they not only convey a correct idea of the shape 




Projection fines 



Fig. ii. 



of an object, but they also carry information as to the size by 
means of dimensions, or measurements written on the various views. 
To be able to read a mechanical drawing, that is, to obtain a 
clear idea of the shape and the size of an object, one must develop 



LESSON No. 11— Continued. 



the faculty of forming a mental picture of it from a study of the 
different views shown on the drawing. He must have sufficient 
imagination to be able to clothe the lines of the drawing with a 
shape. 

One cannot get a clear understanding of an object from looking 
at a single view of a mechanical drawing, but must study all the 
views, looking from one to the other and trying to see the relation 
between them until he gradually grasps their message. 

A knowledge of Orthographic Projection, or the laws by which 
mechanical drawings are made, is absolutely necessary if the student 
is to read a drawing readily and to the best advantage. 

Theoretically an object is always seen through a geometrical 
plane in both perspective and mechanical drawing. 

As a geometrical plane is a rather difficult feature for the be- 
ginner in this work to understand, we shaU use a sheet of glass to 
represent this plane. The sheet of glass is not altogether correct 
as an illustration of a geometrical plane, but it will answer our 
purpose for lack of a better substitute. 

In a perspective drawing, as shown in Fig. 10, the projection 
lines or rays from the viewpoint may form any angle with the 
plane. This must of necessity be so, as the object is seen from a 
single viewpoint. 

According to the laws of Orthographic Projection, by which 
mechanical drawings are made, the projection lines or rays are 
always at right angles to the plane, that is, perpendicular to the 
plane. 

This is one of the vital distinctions between the two methods 
that the student must always keep in mind if he would obtain a 
clear grasp of the subject. 

A perspective drawing is frequently termed a "one-plane draw- 
ing," from the fact that the object is viewed through a single plane, 
while when making a mechanical drawing, theoretically we use a 
plane for each view. 

To illustrate, when laying out the first view of a mechanical 



drawing (say the top view), the plane is between our eye and the 
object, and parallel to the face shown. Under the theory of the 
subject this view is projected toward us onto the plane. The 
end and side views are projected onto planes which parallel and 
lie near these faces. Then these last two planes are swung up on 
a level, or in the same plane, with the plane carrying the top view. 

By this arrangement we are enabled to look at three sides of 
an object at the same time. 

Suppose the student to be looking down directly on the top 
of a box, one side and one end of which are hinged to the top; if 
this side and end are swung up on a level with the top or in the 
same plane, then we would have an illustration of th«- theory of the 
revolution of the geometrical planes. 

From the foregoing the student should note that in mechanical 
drawing the relation between the views is fixed definitely, that while 
the arrangement of the views on the drawing paper is a matter of 
taste, the relative positions of the views to each other cannot be 
changed. 

To make this more clear, Fig. 12 shows three different arrange- 






Fig. 12. 

ments of the views of an object, but the relative positions of the 
views to each other are not changed at all. 

The student should make every effort to get a clear under- 
standing of this lesson, as it is of fundamental importance in a study 
of mechanical drawing. 



LESSON No. 12. 



SHAFT SUPPORT. — Our present lesson is an application of 
the principles given in our previous lesson. In this lesson the student 
is given an opportunity to make use of his recently acquired knowl- 
edge of projection. 

The student will find his work very much simplified if he keeps 
in mind the positions of the planes of projection, and further if he 
will remember that the projection lines are always at right angles 
to these planes. 

When making the mechanical drawing, the student should try 
to imagine just what each surface will look like by itself in the 
form of a view. He will also be obliged to do some thinking, to 
decide how he will indicate the various surfaces and edges and the 
type of lines to use for the purpose. 



THE DRAWING. — On Drawing C-1005 is shown a perspective 
sketch of a shaft support from which the student is expected to make 
a three-view mechanical drawing. 

The three views should consist of the top, the side, and one 
end, say the three surfaces seen in the illustration. 

For the first view, choose the surface which seems to you most 
likely to be an aid in projecting the other views. In this case the 
side view showing the end of the feather key and the hole for the 
shaft is possibly the best view to begin with. 

Arrange these views neatly on the drawing paper, finish each 
view carefully and see that no dimensions are left off, so that 
the final result shall be a drawing which leaves little room for 
criticism. 




class Industrial 



name John W.Roberts oate Feb- 12-/5. 



The Carnegie Institute or Technology 



PITTSBURGH, PA. 



SCALE 



Shaft Support 

dws.ncC.I005 



LESSON No. 13. 



TOOL REST. — This lesson is identical in character with Les- 
son No. 12; the purpose is the same — to give the student an oppor- 
tunity to strengthen his hold on the subject of projection. 

Another point which the student should consider seriously is 
the faculty of mental picturing. He should try to develop his 
imagination by every means within reason, as this faculty is a very 
important factor in the makeup of the successful business man. 

The ability to form a mental image of an object from studying 
the views of a mechanical drawing is the valuable feature of reading 
such drawings, as one who lacks this ability cannot use the drawing 
intelligently. 

The usual operation is reversed in our present lesson, and in 
certain other lessons, as we look at the picture and from this make 
our mechanical drawing. 

This mode of presenting the subject is adopted because of its 
value in helping the student to see with greater clearness the dif- 



ference between the two methods of presentation, but it is also 
used for the reason that it is an easy step for the student from a 
known method to an unknown one. 

THE DRAWING. — The subject of our lesson is the perspective 
sketch of a tool rest shown on Drawing C-1006. From this illus- 
tration the student is expected to make a three-view mechanical 
drawing of the tool rest. 

Let these three views represent the top, one side, and one end. 
There is little choice as to which view to make first; either view 
will do, though the top view cannot be finished until the dovetail 
is drawn in on the end view and then projected to the top view. 

It should be understood that the dovetail groove in the bottom 
of the tool rest runs through from end to end, and that the bolt 
hole on top is run through the thickness of metal. 

See that no dimensions are left off of the finished drawing and 
that the final result is a neat, attractive piece of work. 




CLAS3 Industrial 

tv/iMc John W.Roberts date: F~eb-l8-/5- 



The Carnegie: Institute or Technology 

PITTSBURGH, PA. 



SCALE 



Tool Rest 

Z3tVG.No. C-1006 



LESSON No. 14. 



UNFINISHED VIEWS.— In this lesson we continue our study 
of the subject of projection. We test the student's knowledge of 
the subject by a method that differs in the mode of presentation 
from the two previous lessons, but the principles of projection are 
the same in all cases. 

With one view of an object finished completely and the other 
two views partially, the student will find it necessary to make use 
of his imagination if he is to complete the unfinished views in a 
satisfactory manner. 

The student should study each problem carefully, as it is highly 
desirable tha| he shall be able to prove the correctness of his finished 
work. 

Certain of the lines left off of the unfinished views are hidden 
surface lines, others are solid lines, consequently the student will 
indicate his grasp of the subject by the way in which he finishes 
these views. 



THE DRAWING. — A number of pieces of various shapes are 
shown in Drawing C-1007, some of the views of each piece being 
incomplete. The student is expected to lay out a full-size pencil 
copy of this drawing with all the views properly completed. 

It is suggested that the student make use of projection planes 
as illustrated in Fig. 1, for by means of this aid the problems will 
be greatly simplified and there is less likelihood of the views being 
finished incorrectly. 

Do this work neatly, showing all the necessary hidden surface 
lines and placing on all dimensions as shown, but keep clearly in 
mind the thought that the important feature is to use this work 
as an aid in obtaining a thorough grasp of the principles of projection. 

In Fig. 1, view C is complete; finish A and B. 

In Fig. 2, view B is complete; finish A and C. 

In Fig. 3, view C is complete; finish A and B. 

In Fig. 4, view C is complete; finish A and B. 





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class Industrial 



Mame John W. Roberts date Sept. 22. OZ 



The Carnegie: Institute or Technology 

PITTSBURGH. PA. 



Problems in Projection 

scale Fall Size dwo.no. CJ007 



LESSON No. 15. 



SKETCHING. — Whatever course in mecnanical drawing the stu- 
dent may pursue, he will sooner or later desire to know something about 
sketching, or, at least, he will feel the need of it. 

A knowledge of sketching is exceedingly useful to men of most of 
the trades, and the lessons on this subject have been planned with the 
belief that they may assist the students to use their pencils more freely 
and easily in making simple mechanical drawings free-hand. 

METHOD. — The method that we shall follow, we shall call the 
"Short -stroke Method," from the fact that as we draw a line in any 
direction, it is not made by a single stroke of the pencil, but by a series 
of short strokes. There should be the smallest possible opening be- 
tween the ends of these short lines, and it would be better still if the 
ends were to just touch without overlapping. 

The object of using these short strokes is to enable the student to 
correct an error in direction at any point along the line. The result is 
that the general direction of the line is straight, and though there may 
he slight errors along the line, they in nowise cause any doubt as to 
its meaning. 

PENCILS. — For sketching, a pencil equalling an H or HB in hard- 
ness will give very satisfactory results, though a 2H Koh-i-noor will 
last much better. The latter, however, is just a little too hard except 
when used on Manilla paper. 

Learn to hold the pencil easily and naturally between the first and 
second fingers and the thumb, in a manner very similar to that used in 
writing. 



Do not turn the paper to suit the direction in which a line is to be 
drawn, but fasten it down to the drawing board and try to develop that 
freedom of movement of fingers, wrist, and arm which will enable one 
to draw a line in any direction with equal ease. 

In drawing straight lines as indicated on the illustration, the student 
will soon discover that they are made in certain directions by a move- 
ment of the wrist mainly. In other directions it is mostly a movement 
of the fingers which gives the best results. 

It is quite difficult to make neat circles free-hand, but by putting 
into practice the following suggestions, the student should obtain satis- 
factory results. 

The student should sit upright while drawing, so that he may the 
better get a clear view of his work as a whole. By having the head 
well up over the work, the eyes can direct the movements of the pencil 
better, and they are in a better position to see if the desired shape is 
growing under the pencil, than if held close to the work. Start at a 
point on the left side, as indicated by the arrows, and with short strokes 
form the upper half of the circle. Then, starting at the same point, 
form the lower half in the same manner. 

THE LESSON. — Fasten the drawing paper smoothly to the 
board and divide it into sections, as shown in the illustration. 

The straight lines should be drawn about J inch apart and in the 
directions indicated by the arrows. 

Draw the circles to the sizes shown, without using a rule; try to 
see how nearly correct you can make them by the eye. 



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class Industrial 

name John W. Roberts dat*: Mar. P0- 06. 



The Carnegie: Institute 'or Technology 

PITTSBURGH, PA. 



Sketching 



scale Full S/ze 



a»G.No.C-/008 



LESSON No. 16. 



PROPORTIONS. — It is a very valuable acquirement, when 
sketching, to be able to make the details of a drawing of the proper 
proportions in relation to each other. 

The scale of a sketch is of little importance, provided it is large 
enough to show clearly the piece or pieces we desire to illustrate. But 
that which is of importance is that each piece, or detail of the piece, 
should be drawn to the same scale. 

To obtain this result it is quite necessary that the student should 
train his faculty of observation so as to have a sense of measurement, 



and so that, without the aid of a rule, he may be able to draw a sketch 
approximately to a given size. 

The student will be helped to develop this faculty if, in sketching, 
he practises drawing to a certain scale or to given dimensions. 

LESSON. — Make a neat free-hand full-size drawing of the figures 
shown in the illustration. Draw each figure to the dimensions given, 
as nearly as possible, without using a rule. 

Observe that two views are shown of each piece, and try to see 
the relation between the views. 




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class Indusirial 

name John W.Roberts date Mar. BO. 06. 



The Carnegie: Institute of Technology 

PITTSBURGH, PA. 



Sketching 



~Aj.c Full Size 



DWG.HO.3-/O0g 



LESSON No. 17. 



REFERENCE MATTER.— The information given on Drawing 
C-ioio is a type of reference matter which will be of value to the 
student when laying out many of the future lessons. 

In commercial work it is the custom to give no detail dimen- 
sions for bolts and nuts on what are known as "assembly drawings." 
The diameter of nuts and the diameter and length of bolts are 
usually given so that these items may be ordered. The dimensions 
necessary for drawing these details of a mechanical drawing are 
found in "Data Books," which are made up of a series of reference 
sheets. 

In certain future lessons are shown nuts and bolts, the sizes of 
which are given, but the student will be obliged to use the informa- 
tion given on this reference sheet to obtain the dimensions nec- 
essary to make the drawings of these details. 



Conventional methods of indicating screw threads are also 
given on this reference sheet. The methods shown are among the 
simplest in use and for this reason are very desirable. 

Frequently we have objects to make drawings of, which are of 
such shape that we can illustrate them to the best advantage by 
"breaking" out part of the object. 

The main advantage gained as a rule is that this permits us to 
draw the object to a large scale on a smaller sheet of paper than we 
would otherwise be enabled to do. 

It is always understood that the portion broken out is identical 
with that on each side of the "break." 

The student is expected to lay out a pencil copy of this refer- 
ence sheet, the teacher deciding the question as to sizes of nuts, 
bolts, etc. 




U.S.Std.for Nuts &■ Bolt Heads 



Dia. Across Flats = i^X Bolt dia. + £ 

Corners (Hex.) = Dia. Across Flats X 1. 156 
h - ii (5a.)= .< " ■■ X 1.4-14 

Height of Nut = Bolt dia. 

" " Bolt Head= _s of Dia. Across Flats 

Not U .S jStd. 
Radius R = Bolt dia. 
« R'= I^XBolt dia. 



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Conventional method of 
indicofing screw threads 



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Methods of showing a Break in material 



Round S/oc/c 



Break lines made freehand 



Flat Stock 



R. 



class Industrial 



name. John W. Roberts date Ma r_ 1 6-/5. 



The Carnegie Institute of Technology 

PITTSBURGH, PA . 



Reference Matter 



SCALE 



DWG.No.C- IO/0 



LESSON No. 18. 



FLANGED PULLEY. — The figures on Drawing C-ioii repre- 
sent a side view and a true sectional view of a Flanged Pulley. 

The conventional method of indicating screw threads is used in the 
holes for the set screws; note that the threads appear to be left hand. 
These threads are in reality right hand, and it is desired that the stu- 
dent shall reason out for himself just why it is correct to show the 
threads in this manner. 

This lesson is intended to give the student a clearer conception of 
the subject of sectioning; to help him to make a mental picture of 



what the pulley looks like when cut in half along the vertical center 
line. Make a free-hand sketch of the pulley, copying carefully all 
dimensions and necessary information. From this sketch make a 
full-size pencil drawing of the pulley, placing all dimensions just as 
shown on the illustration. 

When dimensioning a drawing, bear in mind that your drawing is 
to be used as an instrument to furnish exact information to some one 
in the shop, and unless you do your work carefully and accurately, 
costly mistakes may be the result. 





Drills-Tap ^-20 Thd. 
for 4*x £ 'rfd/ss. Set Sc. 



<:lass Industrial 
hame John W. Pch^-fe. 



The Carnegie: Institute or Technology 



Flanged Pulley 



Pate: Oct. 16- OS. 



PITTSBURGH, PA . 



scale Full Size 



oiv&no C-ioil 



LESSON No. 19. 



PROJECTION. — In all of our previous lessons which dealt with 
the subject of projection, we have considered problems in which the 
planes were parallel to the surface projected. 

The major portion of the drawings made in commercial drafting 
rooms are made after this fashion, at the same time there are many 
pieces of such shape that it is necessary to use planes which are 
placed at some other angle to the object than the conventional 
one. 

It naturally follows that the student should be able to place a 
plane in any position in relation to an object, so that he may project 
a certain surface in such manner as to obtain the desired view. 

While the plane may form any angle with the surfaces of the 
object, when the view is projected the projection lines must form 
right angles with the plane just as when the plane is placed in the 
conventional manner. 

The piece used in the illustration is not of a type to need a special 



angle plane, but this simple shape will serve very well to demonstrate 
the principle involved. 

THE DRAWING. — On Drawing C-1012 is shown a partially 
finished problem in projection. View (a) is an end view of a rect- 
angular block with all the dimensions shown; view (b) is a par- 
tially finished, foreshortened top and edge view, showing the length 
of the block. 

View (a) is projected upon a plane which is set at an angle of 
45°; this plane is then raised to a vertical position and swung 
around one-fourth turn or 90 °, so as to show view (b). 

View (c) should be an end view of the block tilted at an angle 
of 45°- 

Lay out the three views full-size, finishing them completely 
and placing them in the positions indicated on the drawing. 

The student should note that the plane between view (b) and 
view (c) is parallel with the end of the block. 




Plane 



Project end view here 

c 



class Industrial ^HE QaRNEGIE INSTITUTE OF TECHNOLOGY 



name: John W. Roberts oatc Oct.IO.07. 



PITTSBURGH, PA. 



... . PV? OJEC TION 
acALz Full Size dshg.no.C.IOIS 



LESSON No. 20. 



GEOMETRICAL PROBLEMS.— Before taking up the follow- 
ing problems in geometrical construction, the student should see 
that the points of his pencil and compass are in first-class 
order, as it is necessary that this work shall be done carefully and 
accurately. 

The main object of this lesson is to familiarize the student with 
certain geometrical terms and their meaning, all of which are used 
frequently in mechanical drawing. This is especially necessary 
for those students who have not studied plane geometry. 

When laying out these problems the student is expected to use 
the following tools only: pencil, both triangles, scale, and large 
compass. 

Fig. i. Bisect (or divide in half) a straight line. 

Fig. 2. Bisect a given arc. 

Fig. 3. Bisect a given angle. 

Fig. 4. Divide a line 2ff inches long into n equal parts. 

Fig. 5. Divide the space between two lines into 13 equal parts, 
the lines to be two inches apart. 

Fig. 6. Circumscribe a circle about a given triangle. Inscribe 
a circle within the same triangle. 

Fig. 7. Through a given point draw a line tangent to a given circle, 
the point being on the circumference of the circle. 

Problems 1, 2, and 3 are of such character that the student 
should be able to solve them without help. 



Fig. 4. To divide a given line into an equal number of parts 
draw a construction line, at any angle and of any length, from one 
end of the line which is to be divided, then using the scale, lay off on 
the construction line the number of parts desired. Now with one 
triangle as a ruling edge, and the other '. as a base, set the ruling 
edge in line with the last point on the construction line and the end 
of the line to be divided and connect these two points. 

All the other points may be projected from the construction line 
to the original line in like manner, keeping the ruling edge parallel 
with the end line. 

Fig. 5 is an adaptation of the construction described for Fig. 4. 
The scale is tilted to an angle which will bring the number of divi- 
sions desired between the lines, then the points are set off opposite 
the graduations representing the unit of division. 

Fig. 6 is a combination of Figs. 1 and 3 and should be within 
the comprehension of the student. 

The student should not have much trouble with Fig. 7, especially 
if he will observe that the point of tangency is located where the 
radius of the circle intersects the tangent line, when these two 
lines are at right angles to each other. 

The ability to make this drawing is of itself of little value, but 
if the student fully grasps the principles involved in these problems 
and applies them to later work, this lesson will be of considerable 
value. 




Poinf 




^ , . , The Carnegie Institute of Technology 

CLASS Ir,dus1r,al PITTSBURGH. f=A. 

i.ame John W.Roberts date. Nov. 20-06. 



Geometrical. Problems 

scale Full Size CrrG. No. C- 10/3 



LESSON No. 21. 



THE ELLIPSE. — Make a neat pencil drawing of an ellipse by 
the three methods indicated, and of the elliptical curve shown on 
Drawing C-1014. 

When drawing the ellipse, make the major or long axis 3^ inches, 
and the minor or short axis 2 inches in each case. 

For Fig. 1, lay off the major and minor axes to the lengths given 
above; take a straight edge made of any suitable material, as card- 
board or wood, and, on one edge, mark off the points AB equal to 
half the minor axis; from A, mark off point C equal to half the major 
axis. Place the straight edge so that the point B comes on the major axis 
and point C on the minor axis ; now, with the pencil, mark a point on 
the drawing paper at A. Shift the straight edge and repeat (keeping 
B and C on the major and minor axes respectively), placing a sufficient 
number of points on the paper to enable you to trace a curve through 
them easily. 



The method illustrated in Fig. 2 is of such a nature that the student 
should be able to solve the problem without assistance. 

Fig. 3 is known as the " Three-radii Method." 

Construct the rectangle ADCEB. Draw the diagonal AC. Through 
D, draw DF at right angles to AC. Then, F is the center for arc 
GCH, and J is the center for arc KAL. 

Make OM= OC. Describe the semicircle AM. 

Make OP= CN. With center F, describe arc RPS. Make AQ= 
ON. Then, with J as center and radius JQ, describe arc intersecting 
arc RPS at T. T is the center for the tangent arc LG. 

To construct the curve shown at Fig. 4, divide the base lines of 
the curve into the same number of equal parts (any number) and con- 
nect these division points by straight lines. The combined outer sur- 
faces of these lines form the desired curve. 



Fig. I 




Fig. 2 




Fig. 4 




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Class Industrial 

mami John HCRotxrr+s DAT £ Dec. IS-06. 



The Carnegie: Institute of Technology 

PITTSBURGH, PA. 



The Ellipse: 



ocalc Full Size 



cws.Afa. C-IOIA 



LESSON No. 22. 



METHOD OF HOLDING PEN.— In learning to trace, one of 
the first problems which confronts the students is how to hold the 
instruments. 

In general, the ruling pen and the pen point of the compass should 
be held in such a manner as to bring the points of both jaws on the 
paper at the same time, as shown at (b) of the illustration, Fig. 13. 




a 



b 



Fig. 13. 



Do not lean the pen either toward the ruling edge or away from it, 
but hold it in a vertical plane, thus obtaining clean even lines free 
from a ragged edge. 

While the pen should not be leaned toward or away from the 
ruling edge, it will be found that the ink will flow more freely if 
the pen is leaned slightly in the direction in which the line is being 
ruled, as shown at (a). 



When using the pen compass for large circles, the legs may be 
bent at the joints, so as to meet these conditions. 

TRACING CLOTH.— The student will find one side of the 
tracing cloth with a glazed or calendered surface, while the other 
side has a dull finish. If the glossy s'de is used, it will be necessary 
to dust the surface with powdered chalk or talcum powder, as the 
ink will not flow freely otherwise. In a great many drafting rooms 
the dull side of the cloth is used from preference, as it takes ink 
very well without powder of any kind, though the powder makes 
the ink flow more freely. 

CARE OF PENS. — A common mistake of most beginners is to 
fill the pen with too much ink, with the result that, before they 
realize it, there is a big blot on their work. This is not necessarily 
caused by the pen being filled too full, but it is frequently the cause. 
It is better to fill the pen oftener and to use less ink at one time. 

Another very good habit to acquire is to wipe out the pen each 
time fresh ink is to be put in, as the ink flows more freely from a 
clean pen than from a dirty one. 

TRACING MACHINE BOLT.— When beginning a tracing 
tack the cloth down carefully over the pencil drawing, then dust 
the surface with powder, using care to wipe off what is left after 
rubbing the tracing cloth with a clean linen rag, then begin by 
adjusting the compass pen to the width of line desired for an out- 
line. In deciding on the width of line, the student should bear in 
mind that to get blue-prints with clear white lines, it is necessary that 
the lines of the tracing be fairly heavy; not the fine "pretty" lines 
that beginners are so prone to use. 

The illustration, Fig. 14, shows the various steps in making a 
tracing: First, throw in all the circles and radii; then, beginning 



LESSON No. 22— Continued. 



at the top, rule in all the horizontal outlines; next, starting at the 



Ol: 




o 




1st. Circles and Radii 



3rd. Vertical lines 





2nd. Horizontal lines 



Dimension lines 



4th. Angular lines. 

Projection lines 




CTho 'per 1> 

5fh. Projection and Dimension lines— 

Dimensions— Notes 
Fig. 14. 

left side, rule in all the vertical outlines; and, finally, rule in the 
angular outlines. 



Now, adjusting the pen to a much finer line, rule in the pro- 
jection lines; these lines for drawings of small figures should be 
composed of dashes f to f inch long, and for large figures 
h to § inch long. Do not let the projection lines touch the figure, 
but leave a slight opening between the end of the line and the 
figure. 

Next, rule in the dimension lines; these lines for drawings 
of small figures should be solid except for the opening left for 
the dimension, but on drawings of large figures they may be 
broken lines of long dashes — the length to suit the size of the 
drawing. 

Now, place the arrow heads on the dimension lines and put in 
the dimensions, using care to make the figures clearly. 

FINISHED DRAWING.— In the finished drawing there should 
be a marked contrast between the weight of the outlines of the 
figure, and of the center, projection, and dimension lines; the latter 
should be decidedly lighter than the outlines. When these various 
lines are drawn to the proper proportions and are well arranged, 
the figure seems to stand out by itself and is much more easily 
understood. 

When the drawing is completed, print the title on neatly and 
carefully, as the looks of a good drawing will be spoiled if the printing 
is done in a careless, slipshod manner. 

Use a Gillott's No. 303 pen point for lettering and dimensioning 
the drawing. 



LESSON No. 23. 



HAND WHEEL. — In our previous lessons on sectioning we have 
dealt with true sections, while, in the present lesson, the sectional view 
shown of the Hand Wheel is what is called a "conventional section." 
In other words, it is not a true section, but a special one which is 
used because it illustrates the shape of the piece more clearly for 
the pattern maker and machinist. The draftsman can lay it out 
more easily and quickly as well — an economy that should be con- 
sidered. 

As an illustration of the convenience of special sections, note the 
conventional section of the arm of the hand wheel; without this section 
it would be pretty hard to give the pattern maker a clear idea as to the 
shape of the arm. 

This conventional method of sectioning is used constantly on draw- 
ings of such pieces as wheels, pulleys, and gears with arms. 



LESSON. — Make a full-size pencil drawing of the Hand Wheel. 

Place all dimensions just as shown, with the exception of those that 
refer to the handle; these dimensions should be left off, as they were 
intended merely as an aid to the student. Mark this part "No. 2 
Handle." When the pencil drawing is complete, make a tracing of it. 
Try to do this work neatly; make the lines of the tracing clear and dis- 
tinct, keeping in mind the instructions given in Lesson No. 22. 

When drawing the ball of the handle, do not try to make the 
two radii (i\ and 1 inch) touch, as they should be joined with a 
tangent straight line. The student should bear in mind that where 
radii swinging in opposite directions are to be joined, a straight 
line should be used for this purpose, otherwise the line appears to 
have a corner or uneven place. Where the radii are small, as at the 
stem of the handle, the rule may be overlooked. 





class Indus trlaf 
hauc John W. Roberts. 



The Carnegie: /nstitute or Technology 



PITTSBURGH, PA. 



8 Hand Wheel 

scale Full Size rvG. noC-IOI5 



LESSON No. 24. 



DRAWING TO SCALE.— In all of our previous lessons, the 
pieces illustrated have been drawn full size; in our present lesson we 
shall take up the subject of drawing objects smaller than full size, or 
"drawing to scale," as it is generally termed. 

In most modern commercial drafting rooms, the drawings are made 
on paper of certain sizes. These standard sizes (usually three or four) 
are adopted to suit the needs of the manufacturer, and each of the 
machine parts built is shown on one of these standard-size sheets. 

Small parts may be drawn full size, but large ones must, of necessity, 
be drawn to a smaller scale, as £ size, i size, and £ size. 

These are the scales usually adopted by manufacturers of machinery. 
The piece is drawn to the scale necessary for clearness and best suited 
to one of the standard-size sheets, while the dimensions are placed in 
the same manner as if the piece were drawn full size. In other words, 
the dimensions must show the sizes to which the piece is to be finished 
in the shop. 

In drawing to a given scale, that scale becomes our unit of measure- 
ment. As an illustration, take our present lesson, in which the student 
is expected to make a half-size drawing of the Lathe Face Plate. 

As £ inch is our unit of measurement, £ inch equals i inch, but 
instead of dividing each dimension by two, read it thus: "if halves 
for if inches, 5 halves for 5 inches, f halves for £ inch, etc." 

If the student will carefully study the illustration in Fig. 19, he 
will observe that the divisions can be made on the scale by simply 
training the eye to perform this operation. 

As an aid in readily locating a dimension on the scale, look for the 
nearest large graduation; the full-size dimension on Fig. 19 is 5|f inches, 
a thirty-second less than 5! inches, which figure can be found at once. 
To find 5§f inches half size, look for 5I inches half size and point back 
toward zero one-half of the space between graduations. To locate 
5|| inches quarter size, look for 5! inches quarter size and point back 
toward zero one-fourth of the space between graduations. 5§§ inches 
one-eighth size is located in the same manner. 



By this method it is necessary for the student to keep but one 
dimension in mind when making a division, and when he learns to 
read his scale properly, he is much less liable to make mistakes t! an if 
he were to make his divisions in the usual way. 



Full Size 



± 

± 
8 



58 



ones 



5§§ halves 



* 5si quarters-^ 
5M eighths 1 



WlWIfFTWlJ^ 



m 



Fig. 15. 

To get a radius for half -size circles, set the-compasses to the dimen- 
sion quarter size. For example, to draw the end view of the hub 4-inch 
diameter half size, take a radius of 4-inch diameter quarter size. 

LESSON. — From the illustration, make a half -size pencil drawing 
of the Lathe Face Plate. 

Section AB is cut along the line AB, and is a conventional method 
of showing a true section along this line. 

Section CD is necessary to give the pattern maker a clear idea of 
the shape of the metal back of the T slot. 

Where dimensions are given in decimals, draw that part to the near- 
est sixty-fourth. 

Study the illustration carefully, so as to get a clear idea of the mean- 
ing of each line. Do not simply copy; try to make a mental picture of 
the shape of the piece- 
Use the edge of your scale, which is graduated in sixteenths, and 
work from dimensions given. 




Section C-D 



Bore 2.034 
Tap 2£~ 6 Thd. 
U. S, Std. 




Section A~B 



class Industrial 
namc John W. Roberts 



The Carnegie Institute or Technology 

PITTSBURGH. PA. 



datc Oct 20- 06, 



Lathe Face Plate 



scale ■$ size 



owa.No.C-1016 



LESSON No. 25. 



ASSEMBLY DRAWINGS.— It is a common practice in most 
drafting rooms to make drawings which show the various parts 
of some mechanism fastened together. These drawings are termed 
"assembly drawings," and they are of decided value to the men in 
the shop who erect or assemble the machines. 

The most important feature of this lesson is this new type of draw- 
ing, which is brought to the student's attention now for the first time. 

Another feature that is important and one which will bear rep- 
etition is that the student is obliged to transpose a perspective 
drawing into a mechanical one, thus causing him to make use of his 
knowledge of orthographic projection. 



LESSON. — Our first assembly drawing is to illustrate the parts 
of a towel roller fastened together. 

From the sketch on Drawing C-1017, the student is expected 
to make a three-view mechanical drawing. These three views 
should represent the top, front, and one end of the towel roller. 

Make this drawing full-size scale, with the exception of the 
length, which should be taken care of by "breaking" out sufficient 
material to allow the views to be arranged properly on the drawing 
paper. 

All hidden surfaces and all necessary dimensions must be shown, 
so that the finished result is a complete working drawing. 




Roller pin 
j dia.X g long 



Material, Maple 
Finish. Natural wood, three coats varnish 



class Industrial 

ma,i*e John W. Roberts date Mar. 13-15. 



The Carnegie Institute of Technology 

PITTSBURGH, PA . 



Id a el Roller 



DHG.SVO-C-IO/7 



LESSON No. 26. 



COUPLING. — From the sketch shown on Drawing C-1018, 
make an accurate half-size pencil drawing and tracing of the Safety 
Flange Coupling. 

This coupling derives its name from the flanges that extend out 
over the bolt heads and nuts, keeping the workman's clothing from 
being caught, thus preventing many serious accidents. 

Note that the shafts are of different diameters and that each 
half coupling is fitted with a taper key. These keys are tapered 
on one side only — that which is set in the hub of the coupling. 
When assembling, the half coupling is forced onto the shaft 
and the keys are fitted before the two halves are bolted together; 
this brings the large end of the key at the end of the shaft, so 
that when the halves are fastened together the keys cannot work 
loose. 



Observe that one-half of the coupling is made with a recess 3! 
inches diameter by | inch deep, to receive the boss on the other half 
coupling; this is for the purpose of keeping the halves in line with 
each other. 

The student should take especial notice of the "Bill of Material" 
shown on the drawing. This is a device to aid the clerical force, 
who usually order the materials from wh ch the mechanism is 
produced. 

When items are not exactly alike they must be given separate 
item numbers. Frequently the same pattern will do for both halves 
of a machine part even though they are finished differently and 
have different item numbers. 

Remember that neat, accurate work is expected, not work done 
in careless fashion. 



Driving fit 
Finish all oven 




Bill of Material 



Item 

No. 


Description end Material 


Pit. No. 


Req. 




(7) 


Half Coupling, C.I. 


A.20I 


1 


= -tt 


© 


• > M a 


a 


1 


t 


® 


§XZ£ Machine Bolt with Nat 




4 







i'xfXJi Taper Key, C.R. 




' / 




® 


&A 2 A ^J/s " " ' 




/ 




f s " > 


„ 


7* 


«- a 'U 




s" 


' g - ■ °- 


1- 





CL/IS3 Industrial 

name John W.Roberts date Nov. 16.06. 



The Carnegie Institute or Technology 
Pittsburgh, pa. 



Safety Flange Coupling 

scale i Size DWG. No. C- 1018 



LESSON No. 27. 



COUPLING. — The assembly drawing used for the present 
lesson is of a "Compression Shaft Coupling." 

This coupling can be clamped around the ends of two shafts, 
the two halves of the coupling being held together by means of the 
bolts shown. The upper half of the coupling is fitted with a key 
which keeps the shafts in line. 

No dimensions are shown for the bolts and nuts used on this 
coupling, but the student will find the diameter of bolts given on 
the drawing and by means of the reference sheet, Lesson No. 17, 
he can calculate the dimensions necessary for laying out these 
parts. 

In laying out the frame for the "Bill of Material," the student 
is expected to use the same dimensions as were given in our previous 
lesson. 

LESSON. — Make a half-size pencil drawing and tracing of the 
coupling shown on Drawing C-1019. 

It is expected that the student will not copy the views as they 



are shown, but will lay them out as follows: Section A-B, to be 
shown as at present, except that the view is to be revolved on its 
axis (clockwise) 90° or one-fourth turn, bringing the bolts horizontal, 
with the nuts on the right-hand side. 

This change in Section A-B will necessitate the lengthwise 
view being revolved on its axis one-fourth turn toward us, bringing 
the ends of the nuts on all six bolts into view. 

It is understood that the dimensions given on the present illus- 
tration are to be used on the rearranged views. 

As a result of these changes the lengthwise view of the coupling 
will present a very different appearance from the present one, con- 
sequently the student will be obliged to reason out for himself just 
how this view will appear, and as he places the lines of the drawing, 
so will he indicate his ability to represent the various surfaces properly. 

While accuracy and neatness are important features of this work, 
mental effort is of equal or greater importance, and the student 
should do all in his power to stimulate the reasoning faculties. 



Peam fit 




<0 



Section A-B 



10' 



K?V 



:^££ 



-*£- 



,7" 



^EJ 



•jP- 



- 2 r. 






^EJ 



-i- 



B/Ll of Material 



Item 
No. 


Description and Material 


Pat No. 


Req. 


O) 


Half Coupling C. 1. 


A. BOO 


1 


®- 


ft »» »> 


»t 


1 


© 


fx2f M.B.Tap Bo/t with Nut 




6 


@ 


fx? e ~x/0"Key 




1 



class Industrial 
Hame John W.Roberts 



date Oct.20-06. 



The Carnegie: Institute of Technology 

PITTSBURGH, PA. 



Compress/on Shaft Coupling 



Scale j Size 



owe /voC/0/9 



LESSON No. 28. 



SPECIFICATION. — In most of our previous lessons the student 
has had a graphic illustration to work from; in our present lesson he 
will have a written description of an object, which for lack of a better 
name we have termed a specification. 

The main purpose of this lesson is to further strengthen the 
student's faculty for making mental pictures, by causing him to make 
a freehand drawing of something not shown, but for which it is 
necessary for him to use his imagination. 

The student is expected to make freehand a two-view sketch 
of the pulley described. He is to complete this sketch fully and 
carefully, with all dimensions, so that using it as a guide he may 
lay out a half-size two-view mechanical drawing. 

When laying out the sectional view, keep in mind the instruc- 
tions given in Lesson No. 23, on the conventional method of sec- 
tioning for pieces of this type. 

PULLEY. — From the following data make a freehand sketch 
showing a side view and a sectional view of the pulley described: 

Diameter of the pulley, 1 foot 2 inches at the crown (or greatest 



inch 



diameter); face or width, 6 inches; taper of crown equals 
per foot. 

Diameter of hub, 3! inches; length of hub, 4 inches; bore, i| 
inches ; with keyway -^ inch wide by -^ inch high. 

Rim to be made with rib around inside where joined to arms. 
Rim J inch thick at edge, and y& thick through crown and rib; 
inside of rim to be straight to arms. 

Number of arms, 6; arms to be ij inches wide by f inch thick 
at xim, and if inches wide by xf inch thick at hub; f-inch fillets 
(or rounded corners) at side of arms at hub, and at side and edge 
of arms at the rim; f-inch radius at the junction of the arms near 
the hub. 

When locating the keyway in the side view showing the end of 
the hub, be sure to place it central with one of the arms, as this 
will give a stronger hub section than if the keyway is placed midway 
between two arms. 

The completed pencil drawing should be given the title of 14" 
Pulley, Drawing C-1020. 



LESSON No. 29. 



ENGINEERING CURVES.— The principle of this lesson is to 
generate the path of a moving point. The curves illustrated are con- 
stantly used in engineering work, and a knowledge of their construction 
should be both interesting and valuable to the student. 

The cycloid is the curve generated by a point on the circumference 
of a circle when rolled along a straight line. When the generating 
circle is rolled upon another circle, an epicycloid will be generated. 

When the generating circle is rolled under another circle, a hypo- 
cycloid will be generated. 

To generate the cycloid mechanically, lay off the base and center 
lines; set the dividers to any short space (so that the length of the 
chord is about equal to the arc), in this instance \ inch, and step off 
16 or 18 points on the base line. Erect perpendiculars through these 
points; swing in the generating circle from these different points, so as 
to place the circle in the different positions which it would assume in 
making one complete revolution. Now, with the dividers, step off on 
the second circle the distance it has rolled along the base line, in this 
case \ inch. Repeat for each new position of the generating circle 
(measuring with the dividers the distance around the circle that it has 
iolled along the base line), until a complete revolution has been made, 
then trace the curve through the points thus found. 

The epicycloid and hypocycloid are generated in the same manner, 



the base circle replacing the base line of the cycloid. 

The involute is the curve generated by every point in a cord as it 
is wrapped upon or unwound from a cylinder. 

To develop the involute mechanically, unwind a little bit of the 
cord at a time, and step off upon the line the distance unwound. 

Set the dividers to \ inch and step off 10 or 12 divisions upon the 
base circle ; from these points draw tangent lines to represent the cord 
in different positions when being unwound. 

The helix or screw is the curve which would be generated upon a 
cylinder revolved at a constant speed against a point, the point moving 
along at a constant speed parallel with the axis of the cylinder. 

To generate this curve mechanically, divide the circumference of 
the cylinder into any number of equal parts, in this case 25, numbering 
these points from the left on the center line, as shown. Divide the pitch 
distance on the cylinder into the same number of equal spaces (25) by 
which the circumference of the cylinder was divided. 

Now locate points on the side view of the cylinder at the intersec- 
tion of the vertical division lines with the horizontal projection lines 
(these lines being projected from the points on the end view of the 
cylinder); then trace the curve through the points thus formed. This 
subject requires very accurate and careful work on the part of the 
student. 



Cycloid 



Involute 




ciAss Industrial 

name John W. Roberts catc Feb. 6.07. 



The Carnegie Institute or Technology 

PITTSBURGH, PA. 



Engineering Curves 
The Path or a Mo v:ng Point 



scale Full Size 



>£>W6.HO. CJ02I 



LESSON No. 30. 



CONIC SECTIONS.— The fundamental principle involved in 
this lesson is the projection of a point. 

A thorough knowledge of this subject is of great value when 
drawing pieces of such shape that it is difficult to project correctly 
the necessary views. From this lesson the student should realize 
that curves and circular figures may be projected in a very simple 
manner if taken point by point. 

The figures shown on Drawing C-1022 illustrate a cone cut by 
a plane in two different ways. When a cone is cut by a plane 
which passes between the apex and the base at any angle (except 
a right angle), the section will be an ellipse. If the cone is cut by a 
plane which is parallel with one side, the section made is a parabola. 

Lay out the cones to the dimensions given. Divide the 
base circle of the top view into any number of points equally 
or unequally spaced; from these points draw lines to the apex; 
now project the lines down onto the side view. The student 



will find it a convenience to make the line spacing on the 
upper half of the top view a duplicate of that on the lower 
half. 

To develop the ellipse, cut the cone as shown; the points made 
by the intersection of the cutting plane with the slope lines should 
then be projected to the same lines in the top view. By connecting 
these points we have a true ellipse. 

The top view of the parabola is projected in the same manner 
as the ellipse. With the top and side views complete, it is quite a 
simple matter to develop the front view point by point, as shown 
in the illustration. 

By this method of projection the student can easily lay out the 
parabolic curve in the front view first, and then draw the cone 
around the curve. 

Do this work very carefully, as one of the valuable points to be 
gained from this lesson is the ability to do accurate work. 




Ellipse 




class Industrial 

name John W. Roberts date Mar.28-07. 



The Carnegie Institute or Technology 
Pittsburgh , pa. 



Conic Sections 



scale Full Size 



DWG NO. C.I 028 



LESSON No. 31. 



ISOMETRIC PROJECTION.— It is frequently necessary for 
the mechanical draftsman to make one-plane projection drawings 
of certain forms of construction. If these illustrations are prepared 
as they would appear from a single viewpoint, they are termed 
perspective drawings. 

Perspective drawings best illustrate this type of work from the 
fact that they represent the object as it would appear to the eye; 
at the same time there are certain disadvantages connected with 
this system. The main objection is that these drawings cannot be 
laid out from dimensions as mechanical drawings are, and this 
one disadvantage is quite serious from the point of view of the 
draftsman. 

Isometric, or equal measure projection, is a fairly satisfactory 
substitute for perspective drawing for certain classes of work. 




is that in the perspective drawing the surface lines converge at a 
certain distance from the object, as shown in Fig. 16, while in the 
isometric drawing these same surface lines are parallel. 

For certain shapes, or at least for some views, isometric drawings 
are not satisfactory, as the figure appears badly distorted and 
unpleasing to the eye, but for most subjects it will be found quite 
satisfactory. 

Isometric Projection is based on the theory that the object is 



Plane 



Perspective 
Fig. 16. 



/sometric 




izd 




Isometric Axes 



Fig. 17. 



This method may be termed approximate perspective, as it rep- 
resents an object in such fashion that it looks approximately as 
it would appear to the eye. The primary difference between two 
drawings of an object, one in perspective and the other in isometric, 



viewed through a plane with which certain main features of the body 
are equally foreshortened. To illustrate, the cube shown in Fig. 
17 is tilted forward until the edges A-B, A-C, and A-D are equally 
foreshortened as seen through the plane. 



LESSON No. 31— Continued. 



This figure also illustrates what are known as the Isometric 
Axes and their origin, as these three edges of the cube (A-B, A-C, 
and A-D) considered as lines, are separated by an equal angular 




^"""Catting Plane 

Fie. 18. 

space and correspond to the three dimensions, length, breadth, 
and height. 

Fig. 1 8 represents a two-view mechanical drawing of a cube, 



from which is projected (orthographically) , an isometric view of 
the cube. This illustration shows the transformation from mechan- 
ical to isometric, the relationship between these two methods, and 
makes clear the sound basis from which isometric projection is 
derived. 

To demonstrate the theory that the surfaces of the body are 
equally foreshortened, we place the cutting plane through points 
B, C and D of the cube, then as the projection plane is located parallel 
with the cutting plane, the portion of the cube cut away (as indi- 
cated by the dash lines in the isometric view) forms a triangular 
pyramid with corners of equal length. 

The student should try to remember the following fundamental 
principles of isometric projection: 

There are three basic lines known as isometric axes; 

Isometric axes are separated by an equal angular space, and 
correspond to the dimensions, length, breadth and height; 

Vertical lines on the object are vertical lines on the drawing. 
Lines parallel on the object are parallel on the drawing. Right 
angles on the object are either 6o° or 120 on the drawing; 

Lines not parallel to one of the isometric axes are termed non- 
isometric lines. Measurements may be made only on isometric 
lines. 

ISOMETRIC DRAWING.— When a drawing has been made 
according to the rules of isometric projection, the isometric lines 
forming this drawing are eighty-one hundredths (.81) of their true 
length. As this necessitates using an isometric scale, it is gen- 
erally considered good practice to use an ordinary scale and to 
lay out the figure to the dimensions given. The result will be an 
isometric drawing, not a projection, but as the only difference is in 
the size of the figure, this is of little importance. 

COORDINATE AXES.— When laying out isometric drawings 
of certain shapes, a very convenient aid is the related axes, 
usually termed coordinate axes. Fig. 19 illustrates this feature, 
as it shows how the isometric view of a triangular pyramid 



LESSON No. 31— Continued 

may be constructed with the aid of these axes and the mechanical 



views. 



To construct Fig. 19, lay out the mechanical views as shown, 



ft 

D A 





Fig. 19. 

then draw a rectangular figure about the top view (as indicated 
by ABCD). This gives a figure that parallels the isometric axes 
and on which we may locate the base of the pyramid. After this 
has been done, find the point of intersection of the axes (1-2 and 3-4) 
on this figure, and from this point erect a perpendicular on which 
lay off the height of the pyramid. Now connect the apex point with 
the corners on the base and the figure is complete. 

To emphasize the convenience of these related axes, the student 



is reminded that measurements may De made only on isometric 
lines, and as the fines for min g the outline of the pyramid base are 
not at right angles with each other, only one side may be placed 
on an isometric axis. 

Fi<*. 20 shows the application of the coordinate axes to quite 
a differentlv shaped figure from our last illustration. The mechan- 




Fig. 20. 

ical view of the side of the piece is divided into a certain number 
of parts (any number), spaced either evenly or unevenly, then 
these lines or axes are used as shown when constructing the iso- 
metric view. Two applications are shown, one of which is pleasing 
to the eye, and the other quite the reverse. 

ISOMETRIC CIRCLES.— The methods of constructing iso- 
metric circles should require little explanation and their application 



LESSON No. 31— Continued. 



to rounded corners should be readily understood from the illus- 
tration, Fig. 21. 

For general purposes the four-center method will be found satis- 
factory, and, with a little study of the illustration, the student 
should be able to apply this method to his work. 

One feature which it is well for the student to bear in mind is 

4 Center Construction 



Round opening as shown 




/Application of 4 Center Method 

FlC. 21. 

that to construct any circle arc, he should lay out an isometric 
square of the circle diameter, as a means of locating the position of 
the radius center. 

BROOM HOLDER. — Fig. 22 shows a two-view mechanical 
drawing of a broom holder. From this illustration the student is 
expected to lay out a full-size isometric drawing of the figure. No 
hidden surfaces need be shown, as this is seldom done in draw- 
ings of this nature. The title is to be "Broom Holder, Drawing 
C-1023." 

The student is expected to lay out a view which shows the top, 






Fig. 23. 



LESSON Xo. 31— Continued. 



the front, and the left-hand end, as this view will be most pleasing 
to the eye. Do not overlook the small screw-holes near the ends, 
as they should be shown. 

No dimensions need be placed upon any of these iso- 
metric drawings unless for some special reason the teacher may 

desire it. 

WALL SHELF.— On Fig. 23 is shown a three-view me- 
chanical drawing of a wall shelf. From the information 
cm-en the student is expected to lav out a quarter-size isometric 
drawing of the object. Show no hidden surfaces, but draw in 



all parts which would be in sight naturally from a single view- 
point. 

The same view suggested for the broom holder will be found 
to be satisfactory, that is, one showing the top, the front and the 
left-hand end. 

To lay out this drawing correctly will require careful workman- 
ship, and the student will find that this subject offers several oppor- 
tunities for making mistakes if he fails to keep in mind the principles 
of isometric drawing. 

The title of this lesson is "Wall Shelf, Drawing C-1024." 



LESSON No. 32. 



TOOL-REST DETAILS.— Most of the parts or details of a 
speed-lathe tool rest are shown on Drawing C-1025; part of these 
details are drawn half size, and the rest full size. 

Make an accurate pencil drawing and tracing of the details 
shown. 

The hand wheel is very similar to one drawn in an earlier lesson, 
with the exception that it is an "offset" wheel, that is, the rim 
is not central over the arms, but set to one side. The necessary 
radii with the location of their centers are shown, so that the 
student should be able to draw this hand wheel without diffi- 
culty. 

When drawing the arms of the hand wheel, bear in mind what 



was said in the earlier hand-wheel lesson, in regard to using a straight 
line for the purpose of joining two curves. 

The student should take note of the "finish mark" used on the 
hand wheel and the tool rest. This symbol indicates that the sur- 
face on which it is placed is to be finished. 

On such pieces as bolts, screws, pins, shafts, spindles, and many 
similar shapes it is not necessary to place a finish mark, as it is under- 
stood that these pieces are usually finished all over. 

Do not overlook any of the dimensions on the various details, 
for you must remember that you are furnishing the man in the shop 
with the necessary information to machine these parts correctly. 

Use great care with the lettering and figures. 



Finish all over- 




'6 Thd.per in. 



Harden 



class Industrial 

name John W.Roberts date Dec. 12-07. 



The Carnegie Institute or Technology 

PITTSBURGH , PA . 



12 Speed Lathe 
Tool Rest Details 



scale £ & Full Size 



ows.«. C-1025 



LESSON No. 33. 



TOOL-REST ASSEMBLY.— Drawing C-1026 is an assembly 
drawing of the complete tool rest. 

This drawing is used for the purpose of showing how the different 
parts are fastened together, or assembled, as it is termed. 

The only parts dimensioned are the stand and clamp, all of the 
other details being machined from Drawing C-1025. This assembly 
drawing is, therefore, used as a detail drawing also, as the stand and 
clamp may be machined from it. 



When drawing the parts that are not dimensioned, the student must 
necessarily refer to the detail drawing to obtain the sizes needed. 

Study the drawing carefully so as to obtain a clear understanding 
of the meaning of each line. Do not simply copy the various lines 
because they are shown on the original; satisfy yourself as to their 
meaning. 

Think for yourself. 




Section A.B 




H 






Detail of Stand 



Drill g-Tap§ -16 Thds. 




Bill or Material 



Item 
No. 


Description and Material 


Pat. No. 


Reg. 





Tool Rest, C.I. 


79 


1 


® 


" Stand, C. 1. 


80 


/ 


@ 


- Base, C.I. 


81 J 


1 


@ 


- Hand Wheel, C.I. 


82 


1 


@ 


■■ Clamp, W.I. 




i 


© 


Clamp Bolt, W. 1. 




1 


© 


Adjusting Screw, C.R. 


' / 


® 


Adj. Screw Lever, C.R. 


| / 



class Industrial 
name John W.RoDerts 



date: Dec. 94-07. 



The Carnegie Institute or Technology 

PITTSBURGH, PA. 



/£ Speed Lathe 
Tool Rest Assembly 

SCALE J Size DWG. No. C_ 1026 



LESSON No. 34. 



TAILSTOCK DETAILS.— Part of the details of a lathe tail- 
stock are shown on Drawing C-1027. 

The sectional view of the spindle shows the taper bore in one 
end, and the method of fastening the bronze nut in the other end. 

The end of the spindle is bored to a taper of approximately 
f inch per foot, or the "Morse Taper," a name by which this par- 
ticular taper is known in shops and drafting rooms. By a taper of 
f inch per foot, we mean that a cylindrical piece 12 inches long and 
1 inch in diameter at the small end will be if inches in diameter at 



the large end. In other words, the piece is f inch larger in 
diameter at one end than at the other. 

By this time the student should be sufficiently familiar with hand 
wheels to need no instruction on this subject. 

The binding screw shown is an illustration which shows the value 
of a knowledge of shop practice. This screw is machined in a lathe 
in the manner shown by the solid lines; after being finished, it is 
placed in a special forming tool, where it is bent to the shape shown 
by the dash lines. Make a tracing of the finished pencil drawing. 



NoB Morse Taper 



ix§z Pin, Req. P 




16 Thd. per in. 



class Industrial 
name. John W. Roberts 



date Dec. 30- 07. 



The Carnegie /institute or Technology 

PITTSBURGH. Pa. 



IP Speed Lathe 
Tailstock Details 



scale Full Size 



DW5.No. C.i '037 



LESSON No. 35. 



TAILSTOCK DETAILS.— The rest of the details of the lathe 
tailstock are shown on Drawing C-1028. 

The square-thread screw is used to move the spindle in and out of 
the tailstock barrel. The manner in which the thread is shown on 
the screw indicates that it is to be cut the full length to the collar. 
The main object in showing the thread in this manner is to save the 
draftsman's time. 

The small key set into the stem of the screw is known as a Wood- 
ruff key. This key resembles a portion of a washer driven into a slot 
milled in the screw. 

The small T-shaped key shown is the spindle key, and is used to 
prevent the spindle from revolving. 

The wrench shown is used to tighten the nut on the clamp bolt, 
thus fastening the tailstock to the bed. 



The tailstock plug, or bell as it is usually termed, is screwed into 
the rear end of the tailstock barrel for the purpose of supporting the 
spindle screw. 

The center illustrated is made of tool steel and hardened. Two of 
these centers are used on each lathe, one being fitted into the tail- 
stock spindle, the other in the nose of the headstock spindle, the 
former being known as the "dead center," the latter as the "live 
center." 

The stem of the center is turned to a taper of approximately f 
inch per foot, or what is known as the Morse taper. 

The small steel oiler is used to drop oil on the centers. 

When making a pencil drawing and tracing of this lesson, do the 
very best work of which you are capable. 




rt\ 



\ *"3i;o I 



J 



iP 










class Industrial THE CaRNEGIE INSTITUTE OF TECHNOLOGY 

PITTSBURGH, PA. 
name: John W. Roberts date Jan. 6-08. 



12 Speed Lathe 
Tailstock Details 

scale Pull Size owe. no. C- I02Q 



LESSON No. 36. 



TAILSTOCK ASSEMBLY. — Drawing C-1029 shows the tail- 
stock completely assembled, with all the details numbered to corre- 
spond with the numbers in the "Bill of Material." 

Where dimensions are not shown on certain parts, the student is 
expected to refer to the detail drawings for the necessary informa- 
tion. 

The saw cut on the side of the tailstock barrel is for the purpose of 



allowing this part to clamp tightly around the spindle when the bind- 
ing screw is tightened down. 

The oil hole shown in the bell should be drilled after it is in place 
in the barrel, as it should of necessity be on the upper side of the bell. 

Make this drawing and tracing very carefully, do not overlook any 
dimensions or notes. Bear in mind that nothing is good enough but 
the best work you are able to do. 



Tap§-I6 Thd. 



Bore 4 Tap I z- 12 Thd 




Bill of Material 



.T> 



Note: For details see Dwgs. C.I0Z7 & C.I028 



Item 
No. 


Description and Material \Pat.No\Req. 


'£ 


Tailstock, C.I. 76 


1 


~W 


Spindle, Corona Steel 




1 


r s 


Screw C.R. with fHex. Nut. 




1 


® 


Bell, CI. 


77 


1 


■-©. 


Hand Wheel, C. 1. 


78 


. / 


© 


Dead Center, Tool Steel 




/ 


® 


Spindle l\ut. Bz. 




/ 


® mX? Woodruff Key, C.R. 




/ 


® 


£ Washer, C.R. 




1 


® 


%YmX£ Spindle Key, C.R. 




1 


@ 


Oiler, C.R. 




1 


^@" 


Binding Screw, C.R. 




1 


© 


tx 6 ' Clamp Bolt with Hex.Nut 




1 


©_ 


Clamp , W. I. 




I 



class Indus/rial 
name: John W. Roberta 



date Jan. 1 9- 08. 



The Carnegie Institute of Technology 

PITTSBURGH, PA. 



12 Speed Lathe 
Tailstock Assembly 

scale -g Size owc.no. CLI029 



LESSON No. 37. 



ARCHITECTURAL DRAWINGS.— Up to the present time 
most of our mechanical drawings have dealt with some form of 
machinery, whereas in the following lessons we shall devote our 
attention to some of the drawings used in building construction. 

In taking up the subject of architectural drawing, we shall deal 
only with some of the simpler phases of this work. Briefly, archi- 
tectural drawings of dwelling houses consist of floor plans, elevations 
and details, with a set of written specifications to cover the materials 
used and the mode of erection. 

For simple dwellings there is little need of detail drawings, as 
such features as doors and windows with frames, stairs with rails 
and posts, may be ordered from a manufacturer of such house 
details. 

Usually an elevation drawing represents some view of a house 
as seen from the outside, as a front elevation, Fig. 24, or a side 
elevation, Fig. 25, but it is sometimes desirable to show a sectional 
elevation, that is, a vertical section as seen from one side. 

In the main, elevation drawings of dwellings are of value to 
show certain vertical measurements, such as the height of foundation 
walls, floors, ceilings, and windows, and in addition to give a general 
idea of the outside appearance. 

Floor plans represent views seen from above when a horizontal 
section is taken through the building, these horizontal sections being 
cut through the windows and doors. 

The floor plans show clearly the plan of arrangement of the 
various rooms, the positions of doors and windows, stairways, closets, 
lighting and plumbing fixtures, etc. 

In addition it is from the floor plans that the builder obtains the 
thickness of walls and partitions, the size of rooms and doors, and 




LESSOX Xo. 37 — Continued. 




^-■• 5 -. 



^oofin^Sy^ 



Fig. 25. 



LESSON No. 37— Continued. 



the various measurements which are necessary, aside from the 
heights given on the elevation drawings. 

In the lessons which follow we shall take up floor plans only, as 
it is not deemed advisable to go into the subject to any greater extent 
in this series of lessons. 

BASEMENT PLAN.— The basement plan, which furnishes us 
with the needed information in regard to the thickness and location 
of the foundation walls of our dwelling house, is shown on Drawing 
C-1030. 

By referring to Figs. 24 and 25, as well as Drawing C-1030, the 
student will note that the foundation walls rest on a base termed a 
"footing," which extends on each side of the walls about 6 inches and 
has a depth of 12 inches. The foundations for the front and rear 
porches are shown in their proper location to the rest of the building. 

The positions and widths of the windows are shown, as well as 



the outside entrance to the cellar, which opens onto the landing of 
the stairway leading from the kitchen to the cellar. 

The double dash lines connecting the front wall with the chimney 
foundation are to indicate the timbers which rest on the two 6-inch 
posts and support the floors above. 

LESSON. — The student is expected to lay out a pencil drawing 
of this basement plan to a scale of \ inch equals 1 foot, as shown on 
Drawing C-1030. This method of indicating the scale is commonly 
used on architectural drawings and should be carefully noted, as 
the methods followed on machinery drawings are not used on draw- 
ings of buildings. 

Take especial note also of the location of the lighting and plumb- 
ing fixtures, the chimney foundations and flues, for it is by a study 
of all of the various details that we may form some idea of the con- 
venience of the basement arrangement. 



Symbols 
^T\ Stone 
EZZi Brick 
BSI n'cod z Plaster 







o> 



?0 

to, 

i 




«l-6«* 



■A. fir r^ U ,-f'^ f^r 1 - 1 



H6h 5-6- 




c^.^s3 In dus tria I 

name John W. Roberts date Mar. 16^ 15. 



The Carnegie Institute or Technology 

PITTSBURGH, PA . 



Residence 
Basement Plan 

SCALE /=/-0 DWG. No.C-IO-30 



LESSON No. 38. 



FIRST FLOOR PLAN.— This plan shows the arrangement 
of the rooms on the first floor with the positions of the various 
fixtures indicated. 

A flight of steps lead up to the porch and a single step from 
the porch into the vestibule, which has outer and inner double 
doors connecting with the front hall. 

From the hall one may enter through sliding doors into the 
parlor, which opens through sliding doors into the dining room. 
A swinging door connects the dining room with the pantry. The 
kitchen is connected with the front hall by a short passageway and 
a door also leads into the pantry. 

The stairway in the front hall leads to the second floor. This 
stairway can be reached also by a flight of steps from the kitchen. 
There is another stairway from the kitchen to the cellar. 

To the left of the haU when entering the front doors is an alcove 
with a seat on each side. Another seat is shown in the bay window 
in the dining room. 

If the student will study this floor plan and at the same time refer 
to the front elevation, Fig. 24, and the side elevation, Fig. 25, he 



will gain a clearer idea of the house plan than if he studies the floor 
plan only. 

LESSON. — Lay out a pencil drawing of the floor plan shown 
on Drawing C-1031, using a scale of J inch equals 1 foot. 

This dwelling is built of brick with 13-inch walls and wood and 
plaster partitions. Where no dimensions are given, these par- 
titions are about 6 inches thick, being formed of 2-inch by 4-inch 
uprights (known as studding) with plaster on each side. 

The student should note carefully the symbols used to indicate 
the positions of the lighting and heating fixtures. The wall and 
ceiling fixtures are for both gas and electric light, while the symbol 
in the grates in the parlor and dining room and near the hearth 
in the kitchen indicates gas only. 

The dash lines at the entrance to the alcove in the front hall, 
and those marked "circular arch," indicate an arch overhead and 
not something below the floor, as one might infer who is familiar 
with drawings of machinery. 

Notice should be taken of the rectangular openings in the room 
partitions, as these openings are the hot-air ducts from the furnace 
to the various rooms. 



-34-0" 



i" 
to 






i - 



" <*>= 



— HsV 



6-10 




T 

u 

0. 



I - 

4^ 



02. C 
.. O 

-f 

u 

I - 

sTT 






u 
u 

i - 

o 



u 

I - 



Co 



cz./4ss industrial 

name John W. Roberts date: Mar- 25.15. 



The Carnegie Institute or i echnologv 



PI T TSBURGH, PA . 



Residence 
First Floor Plan 



LESSON No. 39. 



SECOND FLOOR PLAN.— The student should have little 
difficulty with this floor plan after completing the basement and 
the first floor plans. 

At the head of the stairway is an upper hall from which doors 
lead into all four bedrooms and into the bathroom. There is also 
a door opening from this hall onto the stairway which leads up to 
the attic rooms. 

On the illustration near the head of the stairway is a note which 
reads "Down 16 R"; translated, this means down 16 "risers" or 
steps. 

Note the convenient arrangement of the bedrooms and that 
each of the rooms is supplied with a closet, with an additional one 
located in the hall adjoining the bathroom. 

Three of the bedrooms are heated by the furnace register and 



gas grates, while the other one has the furnace register only. In 
the bathroom the furnace register is located in the floor, instead 
of in the side wall. 

LESSON. — Lay out a neat pencil drawing of the floor plan 
shown on Drawing C-1032, using a scale of | inch equals 1 foot. 

When drawing the outlines of the roofs over the bay window 
and the two porches, let these outlines extend out over the bay 
window and the porches about 12 inches on each of the sides away 
from the wall. 

The shaded section of the stairway joining the broken line indi- 
cates a place where one may pass under, in this case from the land- 
ing, step 5, down into the kitchen. On Drawing C-1031 this same 
feature is illustrated on the stairway leading from the kitchen to 
the cellar. 










'- Cb 



1 — 



o 



class Industrial 



name John W.Roberts date April 6L/5. 



The Carnegie Institute or Technology 

PITTSBURGH. PA. 



Residence 
Second Floor Plan 

SCAL € i"= l-O" DXVS.KO.C-/032- 



LIBRARY OF CONGRESS 



019 945 463 8 



in 



■BBB 



11 

mm 



1 lilllui 



